Generally, a vehicle includes a high voltage battery for supplying driving power and an auxiliary battery for supplying operation power to an internal electrical apparatus (an electric load). Here, a low voltage direct current (DC) to DC converter (LDC) connected to the auxiliary battery and the electrical apparatus down-converts a high voltage of the high voltage battery into a voltage for charging the auxiliary battery when a voltage of the auxiliary battery does not exceed a reference value under a control of a higher controller.
The auxiliary battery serves to supply operation power to electrical apparatus such as lamps, systems, electronic control units (ECUs), and the like, as well as for starting the vehicle.
Lead-acid storage batteries have been mainly used as the auxiliary battery of a vehicle since lead-acid may be recharged and be used even though they are completely discharged. However, a lead-acid storage battery is heavy and has a low charging density, and lead-acid used in the lead-acid storage battery may have adverse environmental effects. Therefore, the lead-acid storage battery has been replaced by a lithium ion battery in an some vehicles.
However, when a lithium ion battery is over-discharged, performance deterioration of the lithium ion battery may appear at the time of recharging the lithium ion battery. Therefore, in order to address this situation, technologies of preventing over-discharge of the lithium ion battery by allowing a battery management system (BMS) to include a relay for preventing the over-discharge have been developed.
There exists a conventional technology of protecting a battery for a vehicle by turning off a relay when the battery for a vehicle is in an over-discharge state. However, this technology may be a technology of simply protecting only the battery for a vehicle, and may not protect the respective controllers in the vehicle that are being operated in an ignition-on state.